1. Field of the Invention
This invention relates to an optical disk having a recording format for a sampled servo system.
2. Description of the Related Background Art
In an optical disk having a recording format for a sampled servo system, a synchronous pattern provided with two marks (pits) is formed on the track in order to obtain a synchronizing signal for reading recorded data. The distance between the two marks is made longer than the maximum inversion interval which is the maximum distance between the marks in the marked portion indicating the data.
The RF signal read by a pickup and output from an optical disk are supplied to a differentiator to obtain the synchronizing signal from the synchronous pattern. A zero-cross point of signal output from the differentiator is detected. The synchronizing signal is thus detected from the zero-cross point. Besides the constitution of detecting the synchronizing signal, an arrangement is made to supply the output read by the pickup to an A/D converter, and to use it for the reproduction of the recorded data on the disk after having digitized it.
However, since the reproduction of recorded data is timed by generating a clock pulse on the basis of the detected synchronizing signal, a problem is inevitably encountered that if the systems for detecting the synchronizing signal and the system for reproducing the data are arranged separately from the output signal of the pickup as described above, each operational timing of the respective systems should be adjusted because the degree of delay in the respective systems differ from each other.